lipids (presentation)

8/20/2019 Lipids (Presentation)

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Structure and

Classifcation o Lipids

ipids is an organic

co!po"nd #o"nd in li$ingorganis!s %ha% is insol"ble

&or only sparingly sol"ble' in(a%er b"% sol"ble in nonpolarorganic sol$en%s.



Figure 19.1 The s%"c%"ral #or!"la o#%hese %ypes o# lipids ill"s%ra%e %he grea%

s%"c%"ral di$ersi%y a!ong lipids.

a at a biologicalwax



T(o co!!on !e%hod e)is%s #or

s"bclassi#ying lipids in%o #a!ilies #or %hep"rpose o# s%"dy. *ne !e%hod "sesbioche!ical #"nc%ion o# a lipid as %he

basis #or classi+ca%ion, and %he o%her!e%hod is based on (he%her or no% a lipidcan be broen do(n in%o s!aller "ni%s%hro"gh basic hydrolysis, %ha% is, reac%ion

(i%h (a%er "nder basic condi%ions. Ahydrolysis reac%ion %ha% occ"rs in basicsol"%ion is called saponi+ca%ion reac%ion.



ased on bioche!ical #"nc%ion, lipids aredi$ided in%o +$e ca%egories:

1. Energy- s%orage lipids &%riacylglycerols'

2. Me!brane lipids &phospholipids,sphingoglycolipids, and choles%erol'

. E!"lsi+ca%ion lipids &bile acids'

4. Messenger acids &s%eroid hor!ones andeicosanoids'

/. Pro%ec%i$e-coa%ing lipids &biological(a)es'



ased "pon (he%her or no%saponi+ca%ion occ"rs (hen a lipid is placed

in basic a"eo"s sol"%ion, lipids aredi$ided in%o %(o ca%egories:

1. aponi+able lipids &%riacylglycerols,

phospholipids, sphingoglycolipids, andbiological (a)es'

2. onsaponi+able lipids &choles%erol,

s%eroid hor!ones, bile acids, andeicosanoids'



Tpes o Fatt !cids

The !os% #re"en%ly enco"n%eredlipid b"ilding bloc is %he s%r"c%"ral"ni% called #a%%y acid. A #a%%y acid is a

na%"rally occ"rring !onocarbo)ylicacid. 3n %er!s o# carbon chain leng%h,#a%%y acids are charac%eried as long-

chain #a%%y acids &C12 %o C25', !edi"!-chain #a%%y acids &C6 and C10', or shor%-

chain #a%%y acids &C4 and C5'.



Saturated and "nsaturatedFatt !cids

7a%%y acids are classi+ed assa%"ra%ed #a%%y acids &7As',

!ono"nsa%"ra%ed #a%%y acids&M87As', or poly"nsa%"ra%ed#a%%y acids &P87As'.

A sa%"ra%ed #a%%y acid is a #a%%yacid (i%h a carbon chain in (hichall carbon-carbon bonds are

single bonds.



The sr"c%"ral #or!"la #or %he 15-

carbon 7A is



A !ono"nsa%"ra%ed #a%%y acid is a

#a%%y acid (i%h a carbon chain in(hich one carbon-carbon do"blebond is presen%.

38PAC: cis-9-oc%adecenoic acid

Co!!on na!e: oleic acid



A poly"nsa%"ra%ed #a%%y acid is a #a%%yacid (i%h a carbon chain in (hich %(oor !ore carbon-carbon do"ble bondsare presen%. 8p %o si) do"ble bondsare #o"nd in bioche!ically i!por%an%

P87As.

38PAC na!e: cis,cis-9,12-oc%adecadienoic acid

Co!!on na!e: linoleic acid



"nsaturated Fatt !cids andDouble#$ond Position

• An o!ega- #a%%y acid is an"nsa%"ra%ed #a%%y acid (i%h i%send!os% do"ble bond %hree carbon

a%o!s a(ay #ro! i%s !e%hyl end.

• An o!ega-5 #a%%y acid is an"nsa%"ra%ed #a%%y acid (i%h i%s

end!os% do"ble bond si) carbona%o!s a(ay #ro! i%s !e%hyl end.



P%sical Properties o Fatt!cids

• a%er sol"bili%y #or #a%%y acids is a direc%#"nc%ion o# carbon chain leng%h; sol"bili%ydecreases as carbon chain leng%h

increases. The sligh% sol"bili%y o# shor%-chain #a%%y acids is rela%ed %o %he polari%yo# %he carbo)yl gro"p presen%. 3n longer-chain #a%%y acids, %he nonpolar na%"re o#

%he hydrocarbon chain co!ple%elydo!ina%es sol"bili%y considera%ions.



• Mel%ing poin%s #or #a%%y acids ares%ongly in<"enced by bo%hcarbon chain leng%h and degreeo# "nsa%"ra%ion &n"!ber o#do"ble bonds presen%'. Ascarbon chain leng%h increases,

!el%ing poin% increases. Thegrea%er %he degree o#"nsa%"ra%ion, %he grea%er %he

red"c%ion in !el%ing poin%s.



&nerg#Storage Lipids'Triaclglcerols

• ipids no(n as %riacylglycerols also#"nc%ion (i%hin %he body as energy-s%orage !a%erials.Triacylglycerols are

concen%ra%ed pri!arily in special cells&adipocy%es' %ha% are nearly +lled (i%h %he!a%erial.

• Triacyglycerols are !"ch !ore e=cien% a%

s%oring energy %han is glycogen beca"selarge "an%i%ies o# %he! can be pacedin%o a $ery s!all $ol"!e.



• 7a%%y acids are %he carbo)ylicacids in$ol$ed in %riacylglycerol#or!a%ion. 3n %he es%eri+ca%ionreac%ion prod"cing a%riacylglycerol, a single !olec"le

o# glycerol reac%s (i%h %hree #a%%yacid !olec"les; each o# %he %hreehydro)yl gro"p presen% is

es%eri+ed.



T(o general (ays %o represen%%he s%"c%"re o# %riacylglycerol



Figure 19.( %r"c%"re o# %he si!ple %riacylglycerolprod"ced #ro! %he %riple es%eri+ca%ion reac%ionbe%(een glycerol and %hree !olec"les o# s%earic acid.



•

A si!ple %riacylglycerol is a%ries%er #or!ed #ro! %hees%eri+ca%ion o# glycerol (i%h

%hree iden%ical #a%%y acid!olec"les.

• A !i)ed %riacylglycerol is a

%ries%er #or!ed #ro! %hees%eri+ca%ion o# glycerol (i%h!ore %han one ind o# #a%%y acid

!olec"le.



Fats and )ils

• 7a%s are na%"rally occ"rring !i)%"reso# %riacylglycerol !olec"les in (hich!any di>eren% inds o#

%riacylglycerol !olec"les are presen%

• *ils are also na%"rally occ"rring!i)%"res o# %riacylglycerol !olec"les

in (hich %here are !any di>eren%inds o# %riacylglycerol !olec"lespresen%.



Addi%ional generalia%ion and co!parisonsbe%(een #a%s and oils #ollo(.

1. 7a%s are co!posed largely o# %riacylglycerol in(hich sa%"ra%ed #a%%y acids predo!ina%e,al%ho"gh so!e "nsa%"ra%ed #a%%y acids arepresen%. "ch %riacylglycerols can pacclosely %oge%her beca"se o# %he ?lineari%y@ o#%heir #a%%y acid chains. *ils con%ain%riacylglycerols (i%h larger a!o"n%s o# !ono-and poly"nsa%"ra%ed #a%%y acids %han %hose in#a%s. "ch %riacylglycerols canno% pac as%igh%ly %oge%her beca"se o# ?bends@ in %heir#a%%y acid chains.



a at an oil



2. 7a%s are generally ob%ained #ro!ani!als; hence %he %er! ani!al #a%.Al%ho"gh #a%s are solids a% roo!%e!pera%"re, %he (ar!er body%e!pera%"re o# %he li$ing ani!al

eeps %he #a% so!e(ha% li"id&se!i-solid' and %h"s allo(s #or!o$e!en%. *ils %ypically co!e #ro!

plan%s, al%ho"gh %here are also +shoils. A +sh (o"ld ha$e so!e serio"sproble!s i# i%s %riacylglycerols

?solidi+ed@ (hen i% enco"n%ered



*+ood Fats, -ersus *$ad Fats,

• 7a% is "sed as a s"bs%i%"%e #or %he %er! %riacylglycerol. Th"s a die%ary #a% can be ei%her a ?#a%@ or an ?oil.@

• a%"ra%ed #a%s are ?bad #a%,@ !ono"nsa%"ra%ed #a%sare ?good #a%,@ and poly"nsa%"ra%ed #a%s can be bo%h

?good #a%@ and ?bad #a%.@• %"dies indica%e %ha% sa%"ra%ed #a% can increase hear%

disease ris,%ha% !ono"nsa%"ra%ed #a% can decreasebo%h hear% disease and breas% cancer ris, and %ha%poly"nsa%"ra%ed #a% can red"ce hear% disease ris b"%pro!o%e %he ris o# cer%ain %ypes o# cancers.

• Die%ary #a%s are high in ?good@ !ono"nsa%"ra%ed#a%%y acids incl"de oli$e, a$ocado, and canola oils.



)ega#/ and )ega#0 Fatt!cids

• The 3n"i% die% is high ino!ega- #a%%y acids&#ro! +sh'.

• 8.. die% is high ino!ega-5 #a%%y acids&#ro! plan% oils.'



• Cold-(a%er +sh, also called #a%%y +sh

beca"se o# %he e)%ra a!o"n%s o# #a%%hey ha$e #or ins"la%ion agains% %hecold, con%ain !ore o!ega- acids%han leaner, (ar!-(a%er +sh.

• 7a%%y +sh incl"de albacore %"na,sal!on, and !acerel. eaner, (ar!-(a%er +sh, (hich incl"de cod, ca%+sh,halib"%, sole, and snapper, do no%appear %o o>er as grea% a posi%i$ee>ec% on hear% heal%h as do %heir

?#a%%er@ co"n%erpar%s.



&ssential Fatt !cids

• An essen%ial #a%%y acid is a #a%%y acid needed in %heh"!an body %ha% !"s% be ob%ained #ro! die%aryso"rces beca"se i% canno% be syn%hesied (i%hin %hebody, in ade"a%e a!o"n%s, #ro! o%her s"bs%ances.

• There are %(o essen%ial #a%%y acids: linoleic acid andlinolenic acid. inoleic acid is %he pri!ary !e!ber

o# %he o!ega-5 acid #a!ily, and linolenic acid is %hepri!ary !e!ber o# o!ega- acid #a!ily.

•

These %(o acids &1' are needed #or proper!e!brane s%r"c%"re and &2' ser$e as s%ar%ing!a%erials #or %he prod"c%ion o# se$eral n"%ri%ionallyi!por%an% longer-chain o!ega-5 and o!ega- acids.



inoleic acid is %he s%ar%ing !a%erial #or %he biosyn%hesiso# arachidonic acid.

• inoleic acid &16:2' arachidonic acid &20:4'

*!ega-5 #a%%y acids

Arachidonic acid is %he !aor s%ar%ing !a%erial #oreicosanoids s"bs%ances %ha% help reg"la%e blood

press"re, clo%%ing, and se$eral o%her i!por%an% body#"nc%ions.

inolenic acid is %he s%ar%ing !a%erial #or %hebiosyn%hesis o# %(o addi%ional o!ega- #a%%y acids.

inolenic acid &16:' EPA &20:/' DBA &22:5'*!ega- #a%%y acids

EPA &eicosapen%aenoic acid' and DBA&docosahe)aenoic acid' are i!por%an% cons%i%"en%s o#%he co!!"nica%ion !e!branes o# %he brain and are

necessary #or nor!al brain de$elop!en%. EPA and DBA



C%eical eactions oTriaclglcerols

• Bydrolysis

Triacylglycerol hydrolysis

re"ires %he presence o# anacid or base. 8nder acidiccondi%ions, %he hydrolysis

prod"c%s are glycerol and #a%%yacids. 8nder basic condi%ions,%he hydrolysis prod"c%s are

glycerols and #a%%y acid sal%s.



• 3n si%"a%ions (hereall %hree #a%%y acids

are re!o$ed, %hehydrolysis processis re#erred %o asco!ple%e

hydrolysis.

3# one or !ore o#%he #a%%y acid

resid"es re!ainsa%%ached %o %heglycerol, %hehydrolysis processis called par%ialhydrolysis.



• aponi+ca%ioneac%ion carried o"% in an

alaline &basic' sol"%ion.7or #a%s and oils, %he

prod"c%s o# saponi+ca%ionare glycerol and #a%%yacid sal%s.



• The o$erall reac%ion o# %riacylglycerol

saponi+ca%ion can be %ho"gh% o# asocc"rring %(o s%eps. The +rs% s%ep is %hehydrolysis o# %he es%er linages %o prod"ceglycerol and %hree #a%%y acid !olec"les:

7a% or oil B20 #a%%y acids glycerol

• The second s%ep in$ol$es a reac%ionbe%(een %he #a%%y acid !olec"les and %he

base &"s"ally a*B' in %he alalinesol"%ion. This is an acid-base reac%ion %ha%prod"ces (a%er pl"s sal%s:

#a%%y acids a*B #a%%y acid sal%s

B2*



• Bydrogena%ion

Che!ical reac%ion %ha% in$ol$eshydrogen addi%ion across carbon-carbon!"l%iple bonds, (hich increases %hedegree o# sa%"ra%ion as so!e do"ble

bonds are con$er%ed %o single bonds.

Many #ood prod"c%s are prod"ced $iapar%ial hydrogena%ion. 3n par%ial

hydrogena%ion, so!e, b"% no% all, o# %hedo"ble bonds presen% are con$er%ed in%osingle bonds. 3n %his !anner, li"ids&"s"ally plan% oils' are con$er%ed in%o

se!i-solid !a%erials.



• *)ida%ion

The carbon-carbon do"blebonds presen% in %he #a%%y acid

resid"es o# a %riacylglycerolare s"bec% %o o)ida%ion (i%h!olec"lar o)ygen &#ro! air' as

%he o)idiing agen%.



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